Вопрос: How can I enable telnet access?
Ответ: On some devices you can use this URL: http://DEVICE IP:HTTP port/cgi-bin/configManager.cgi?action=setConfig&Telnet.Enable=true . You will need a valid username and password for this operation to succeed.

There are two reasons that will make gDMSS (DMSS Android version) show you this error message:
-you have entered a bad password: please check it / retype it
-someone has tried to access your account and it got locked

In both cases after you check that the username and the password are the right ones you should reboot your device!

Broadly speaking, there are two simple ways to reset your IP Camera:
-using an external reset button, if the camera provides one
-using an internal reset button — you will have to disassemble the camera for this